Maxwell-filtered local drag ($(1+\lambda {\partial }_t)\mathbf{f}=-D\mathbf{u}$)

A prescribed local linear Maxwell force law filters a harmonic drag amplitude by $(1+i\omega \lambda {)}^{-1}$. For periodic states its time derivative has zero mean, so the mean force equals the mean driving force. Leading harmonic power is reduced by $[1+(\omega \lambda {)}^2{]}^{-1}$, as elastic storage changes the in-phase dissipative response.